(1) Field of the Invention
The present invention relates to a novel method and compositions for the degradation of aliphatic halogenated hydrocarbons into carbon dioxide or other harmless products by the use of a Pseudomonas metabolite(s) and microbial cells. In particular, the present invention relates to the degradation of carbon tetrachloride into carbon dioxide or other harmless products using the metabolite(s). The degradation can be accomplished in various defined media and also in the environment, particularly in contaminated aquifer solutions and soil.
(2) Description of Related Art
The ability of a wide variety of microorganisms to dehalogenate various compounds such as carbon tetrachloride (CT) is well known, and it has been demonstrated that this ability can be exploited for the remediation of contaminated water, waste streams, soil, and air. Typically, microbial CT transformations produce chloroform, which is even more persistent than CT and also poses health and cancer risks. Therefore, remediation strategies that avoid chloroform production are advantageous.
Previous nonbiological strategies for the remediation of sites contaminated with CT involve the extraction of groundwater coupled with above ground treatment by air stripping or adsorption to activated carbon. Air stripping uses large volumes of air to flush and dilute carbon tetrachloride and other volatile compounds out of water, while adsorption of organic contaminants to activated carbon binds the contaminant to a solid material for future disposal. These methods simply transfer carbon tetrachloride from one medium to another without destroying the contaminant.
Previous biological technologies include the stimulation of the indigenous microorganisms at a site to remove the contaminant. The advantage of this technology is the organisms are already adapted to the site and there are no problems associated with the delivery of a microorganism to the site. However, a disadvantage of this technology is that the organisms present may not be capable of degrading the contaminant or undesirable end products may result from the transformation. Another possibility involves augmenting the site with an organism that has been demonstrated to destroy the contaminant of interest under laboratory conditions. The advantage of this method is the organism and the mechanism of transformation can be understood and therefore modulated. However, the disadvantage of this technology is that the fate of the microorganism at the site is unknown. Typically, the introduced organism is incapable of competing with indigenous organisms, and colonization of the site by this introduced organism may be unobtainable.
The prior art has described the use of bacteria to biodegrade various compounds, particularly aliphatic halogenated hydrocarbons such as carbon tetrachloride. Thus, one of the herein listed inventors, Criddle, C. S., et al in Applied and Env. Microbiology 56, 3240-3246 (1990) describe the use of Pseudomonas KC for this purpose in axenic cultures without identifying the particular strain by deposit number. Application Ser. No. 08/062,072, now abandoned, describes the use of Pseudomonas KC under alkaline conditions to facilitate the growth of this bacterium over those present in the environment. This research is also described by Tatara, G. M., et al 59, 2126-2131 (July 1993) along with a discussion of the results with those metals.